Languages › German Two-Way Prepositions Part 3: Horizontal / Vertical Share Flipboard Email Print Hinterhaus Productions / Getty Images German Vocabulary History & Culture Pronunciation & Conversation Grammar By Hyde Flippo German Expert Hyde Flippo taught the German language for 28 years at high school and college levels and published several books on the German language and culture. our editorial process Hyde Flippo Updated January 30, 2019 Believe it or not, two German accusative/dative prepositions make yet another distinction that English does not! The common prepositions an and auf can both mean "on" or "at" but they differ in how they are applied to surfaces. If an object is on or near a vertical surface (a wall, a chalkboard, etc.), then usually the prepositionan is used. If a horizontal surface (a tabletop, a floor, etc.) is involved, then auf is used to express "on" or "at." Look at the illustrations below... Horizontal and Vertical "ON" or "AT"AN (vertical) and AUF (horizontal) AN > VERTICAL - SENKRECHT die Wand • the wall An object approachinga vertical surface.The accus. phrase "an die Wand"answers the question wohin? An object "on" or "at"the wall. (vertical surface)The dative phrase "an der Wand"answers the question wo? AUF > HORIZONTAL - WAAGERECHT der Tisch • the table An object approachinga horizontal surface.The accus. phrase "auf den Tisch"answers the question wohin? An object "on"the table. (horizontal surface)The dative phrase "auf dem Tisch"answers the question wo? Now, if you've been paying attention, can you say what the dative prepositional phrase an dem Tisch or am Tisch means? Unlike auf dem Tisch, an dem Tisch means "at" or "next to" the table. If you are sitting at the table, you are am Tisch. If you are sitting on top of the table, you are auf dem Tisch! German is being very consistent here. If you are talking about your location in relation to the vertical part of the table (the legs, etc.), then you use an. If you're talking about your location in relation to the horizontal top of the table, then you use auf. This logic also applies to expressions like an der Donau (on the Danube). The use of an refers to being on the edge of the river. If we're actually on the Danube (in a boat), then we're auf der Donau. More Examples (A = accus., D = dative)Here are some examples of the uses of an and auf: wo? an der Ecke D - on/at the cornerwohin? an die Ecke A - to the cornerwo? an der Grenze D - on/at the borderwohin? an die Grenze A - to the borderwo? am Rhein D - on the Rhinewohin? an den Rhein A - to the Rhinewo? auf dem Dach D - on the roofwohin? auf das Dach A - onto the roof Idiomatic ExpressionsBesides their "normal" uses, an and auf are also used in many idiomatic expressions and verbal phrases. Here are some examples: auf der Bank - at the bankjemandem auf der Tasche liegen - to live off of someoneauf der Straße liegen A - to be down and outjemanden an der Nase herumführen - to lead someone around by the nose, take them for a foolworan liegt das? - what's the reason for that? Most of the other two-way prepositions are used in idiomatic expressions as well. Related Links The Four German CasesA guide to the four German cases: Accusative, Dative, Genitive and Nominative. Includes cases and the two-way prepositions. A guide to the many ways to say "by" in German. Prepositional PitfallsPotential problems and how to avoid them.